Modified diene elastomer comprising a diene elastomer coupled by an aminoalkoxysilane compound and having an amine function at the chain end, and rubber composition comprising same

ABSTRACT

The invention relates to a modified diene elastomer comprising predominantly the entity functionalized in the middle of the chain by an alkoxysilane group, optionally partially or completely hydrolyzed to give silanol, bearing a tertiary amine functional group and the silicon atom of which bonds the two pieces of the chain, the chain ends of the modified diene elastomer being functionalized to at least 70 mol %, with respect to the number of moles of chain end, by an amine functional group.

This application is a 371 national phase entry of PCT/EP2014/066674,filed 4 Aug. 2014, which claims benefit of French Patent Application No.1357908, filed 9 Aug. 2013, the entire contents of which areincorporated herein by reference for all purposes.

BACKGROUND

1. Field

The invention relates to a modified diene elastomer comprisingpredominantly the diene elastomer functionalized in the middle of thechain by an alkoxysilane group, optionally hydrolysed, bearing atertiary amine functional group and functionalized at the chain end byan amine group. The invention also relates to a process for thepreparation of such a modified diene elastomer, to a compositioncomprising it, and to a semi-finished article and a tire comprising thiscomposition.

2. Description of Related Art

Now that savings in fuel and the need to protect the environment havebecome a priority, it is desirable to produce mixtures having goodmechanical properties, in particular good stiffness and a hysteresiswhich is as low as possible in order to be able to process them in theform of rubber compositions which can be used in the manufacture ofvarious semi-finished products participating in the composition of tirecasings, such as, for example, underlayers, sidewalls or treads, and inorder to obtain tires having a reduced rolling resistance.

The reduction in the hysteresis of the mixtures is an ongoing objectivewhich has, however, to be done while retaining the suitability forprocessing, in particular in the raw state, of the mixtures.

Many solutions have already been experimented with in order to achievethe objective of fall in hysteresis. Mention may in particular be madeof the modification of the structure of diene polymers and copolymersfor the purpose of polymerization by means of functionalization agentsor else the use of functional initiators, the aim being to obtain a goodinteraction between the polymer, thus modified, and the filler, whethercarbon black or a reinforcing inorganic filler.

Mention may be made, by way of illustration of this prior art, of theuse of diene elastomers functionalized by alkoxysilane compounds bearingan amine functional group.

Mention may be made of Patent FR 2 867 477 A1, which claims thefunctionalization at the chain end with compounds of(dialkylaminoalkyl)trialkoxysilane, and also a rubber composition basedon silica or carbon black. Mention may also be made of U.S. Pat. No.8,071,689 B2 and U.S. Pat. No. 8,106,130 B2, which respectively claim,for one, the functionalization at the chain end with the trialkoxysilanecompound bearing a nitrogen-based group, the nitrogen atom beingincluded in a substituted or unsubstituted aromatic heterocycle, and,for the other, with an alkoxysilane bearing an amine functional grouphaving at least one alkoxysilyl group and at least two tertiary aminegroups. Finally, mention may be made of Patent ApplicationWO2009133068A1, which indicates that the functionalization in the middleof the chain with an alkoxysilane compound bearing a secondary ortertiary amine functional group makes it possible to improve the rawprocessing/hysteresis compromise in comparison with a functionalizationat the chain end.

Provision is made, in Patent JP4655706B2, to combine thefunctionalization of the living chain end with a compound of thealkoxysilane type bearing an amine functional group with the initiatingwith an amine-functional alkyllithium with the aim of minimizing thehysteresis. In the same way, provision is made, in Patent ApplicationUS20120245275A1, to combine the functionalization of the living chainend with a compound of the alkoxysilane type bearing an amine functionalgroup with the initiating with a lithium amide but also with thecopolymerization with a functional monomer of the vinylaminosilane type.

These functionalized elastomers have been described in the prior art aseffective in reducing hysteresis. Nevertheless, it turns out that thecompositions comprising elastomers thus modified do not always exhibit asatisfactory hysteresis, an acceptable processing and mechanicalproperties satisfactory for use as tire tread.

For this reason, research studies have been carried out on otherfunctionalization reactions for the purpose of obtaining rubbercompositions having an improved raw processing/hysteresis/stiffnesscompromise.

SUMMARY

The aim of the present invention is thus to provide such a composition.One objective is in particular to provide a functionalized elastomerwhich interacts satisfactorily with the reinforcing filler of a rubbercomposition containing it in order to minimize the hysteresis thereof,while retaining an acceptable raw processing and a satisfactorystiffness, for the purpose in particular of use in a tire tread.

This aim is achieved in that the inventors have just discovered,surprisingly, during their research studies, that a diene elastomermodified by coupling by means of an agent bearing at least one tertiaryamine functional group and an alkoxysilane functional group, which canor cannot be hydrolysed to give a silanol, and the two chain ends ofwhich are functionalized to at least 70 mol % by an amine functionalgroup, confers, on the compositions comprising it, a noteworthy andunexpected improvement in the hysteresis/stiffness/raw processingcompromise.

This is because, on the one hand, the hysteresis/stiffness compromise ofsuch compositions is improved with respect to that of compositionscomprising elastomers not having an amine functional group at the chainend, in particular with respect to that of compositions comprising dieneelastomers modified by coupling by means of an agent bearing at leastone tertiary amine functional group and an alkoxysilane functional groupbut not having an amine functional group at the chain end. Moreover, theraw processing of such compositions is similar to that of compositionscomprising non-functionalized elastomers and remains acceptable.

A subject-matter of the invention is thus a modified diene elastomercomprising predominantly the entity functionalized in the middle of thechain by an alkoxysilane group, optionally partially or completelyhydrolysed to give silanol, bearing a tertiary amine functional groupand the silicon atom of which bonds the two pieces of the chain, thechain ends of the modified diene elastomer being functionalized to atleast 70 mol %, with respect to the number of moles of chain end, by anamine functional group.

Another subject-matter of the invention is a process for the synthesisof said modified diene elastomer.

Another subject-matter of the invention is a reinforced rubbercomposition based on at least one reinforcing filler and on an elastomermatrix comprising at least said modified diene elastomer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 show the dynamic properties and the Mooney viscosity ofcompositions comprising different diene elastomers.

DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENTS

In the text, the expressions “alkoxysilane bearing a tertiary aminefunctional group” and “aminoalkoxysilane” have the same meaning and canboth be used without distinction.

In the present description, unless expressly indicated otherwise, allthe percentages (%) shown are % by weight. Furthermore, any interval ofvalues denoted by the expression “between a and b” represents the rangeof values extending from more than a to less than b (that is to say,limits a and b excluded), whereas any interval of values denoted by theexpression from a to b″ means the range of values extending from a up tob (that is to say, including the strict limits a and b).

The term “functionalization of the chain ends to at least 70 mol % by anamine functional group” is understood to mean, according to anembodiment of the invention, a molar degree of functionalization at thechain end of at least 70%, with respect to the number of moles of chainend. In other words, after the polymerization of the monomers, at least70 mol % of the living chains synthesized bear, at the non-reactive endof the chain, an amine functional group resulting from thepolymerization initiator.

This thus means that at least 70 mol % of the chain ends of the modifieddiene elastomer which is a subject-matter of an embodiment of theinvention are functionalized by an amine functional group and that, inparticular, at least 70 mol % of the chain ends of the entityfunctionalized in the middle of the chain by an alkoxysilane group,optionally partially or completely hydrolysed to give a silanol, bearinga tertiary amine functional group and the silicon atom of which bondsthe two pieces of the chain, are functionalized by an amine functionalgroup.

It should be specified that it is known to a person skilled in the artthat, when an elastomer is modified by reaction of a functionalizationagent with the living elastomer resulting from an anionic polymerizationstage, a mixture of modified entities of this elastomer is obtained, thecomposition of which depends in particular on the proportion of reactivesites of the functionalization agent with respect to the number ofliving chains. This mixture comprises entities functionalized at thechain end, coupled, star-branched and/or non-functionalized.

In the present description, the term “entity coupled” or “elastomercoupled” by an agent bearing a tertiary amine functional group and analkoxysilane functional group, which can or cannot be hydrolysed to givesilanol, is understood to mean the elastomeric entity having thefunctional group within its elastomer chain, the silicon atom of thisgroup bonding the two pieces of the chain of the diene elastomer. It isthen said that the elastomer is coupled or alternatively functionalizedin the middle of the chain, in contrast to the position “at the chainend”, although the group is not located precisely at the middle of theelastomer chain.

The elastomer according to an embodiment of the invention can alsocomprise the other entities functionalized or not functionalized by theaminoalkoxysilane group. When the functional group is located at a chainend, it will then be said that the entity is functionalized at the chainend. The silicon atom of this group is directly bonded to the chain ofthe diene elastomer. When the functional group is central, to which nelastomer chains or branches (n>2) are bonded, forming a star-branchedstructure of the elastomer, it will then be said that the entity isstar-branched. The silicon atom of this group bonds the n branches ofthe modified diene elastomer to one another.

In the present patent application, “predominantly” or “predominant”, inconnection with a compound, is understood to mean that this compound ispredominant among the compounds of the same type in the composition,that is to say that it is the one which represents the biggest fractionby weight among the compounds of the same type. Thus, for example, apredominant elastomer is the elastomer representing the biggest fractionby weight, with respect to the total weight of the elastomers in thecomposition. In the same way, a “predominant” filler is thatrepresenting the biggest fraction by weight, with respect to the totalweight of the combined fillers of the composition. Also, a “predominant”functional entity of a modified diene elastomer is that representing thebiggest fraction by weight among the functionalized entitiesconstituting the diene elastomer, with respect to the total weight ofthe modified diene elastomer. In a system comprising just one compoundof a certain type, the latter is predominant within the meaning of thepresent invention.

The expression “composition based on” should be understood as meaning acomposition comprising the mixture and/or the reaction product of thevarious constituents used, some of these base constituents being capableof reacting or intended to react with one another, at least in part,during the various phases of manufacture of the composition, inparticular during the crosslinking or vulcanization thereof.

As explained above, a subject-matter of an embodiment of the inventionis a modified diene elastomer comprising predominantly the entitycoupled by an agent bearing a tertiary amine functional group and analkoxysilane functional group, which can or cannot be hydrolysed to givesilanol, the silicon atom bonding the two pieces of the chain and thetwo chain ends of which are functionalized to at least 70 mol % by anamine functional group.

The term “diene elastomer” should be understood, in a known way, asmeaning an (one or more is understood) elastomer resulting at least inpart (i.e., a homopolymer or a copolymer) from diene monomers (monomersbearing two conjugated or non-conjugated carbon-carbon double bonds).More particularly, the term “diene elastomer” is understood to mean anyhomopolymer obtained by polymerization of a conjugated diene monomerhaving from 4 to 12 carbon atoms or any copolymer obtained bycopolymerization of one or more conjugated dienes with one another orwith one or more vinylaromatic compounds having from 8 to 20 carbonatoms. In the case of copolymers, the latter comprise from 20% to 99% byweight of diene units and from 1% to 80% by weight of vinylaromaticunits.

The following in particular are suitable as conjugated dienes which canbe used in the process in accordance with an embodiment of theinvention: 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-di(C₁ to C₅alkyl)-1,3-butadienes, such as, for example, 2,3-dimethyl-1,3-butadiene,2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1,3-butadiene or2-methyl-3-isopropyl-1,3-butadiene, phenyl-1,3-butadiene, 1,3-pentadieneand 2,4-hexadiene, and the like.

The following in particular are suitable as vinylaromatic compounds:styrene, ortho-, meta- or para-methylstyrene, the “vinyltoluene”commercial mixture, para-(tert-butyl)styrene, methoxystyrenes,vinylmesitylene, divinylbenzene and vinylnaphthalene, and the like.

The diene elastomer of the composition in accordance with an embodimentof the invention is preferably selected from the group of highlyunsaturated diene elastomers consisting of polybutadienes (BRs),synthetic polyisoprenes (IRs), butadiene copolymers, in particularcopolymers of butadiene and of a vinylaromatic monomer, isoprenecopolymers and the mixtures of these elastomers. Such copolymers aremore particularly butadiene/styrene copolymers (SBRs),isoprene/butadiene copolymers (BIRs), isoprene/styrene copolymers (SIRs)and isoprene/butadiene/styrene copolymers (SBIRs). Among thesecopolymers, butadiene/styrene copolymers (SBRs) are particularlypreferred.

The entity functionalized in the middle of the chain by an alkoxysilanegroup, optionally partially or completely hydrolysed to give silanol,bearing a tertiary amine functional group, the silicon atom of whichbonds the two pieces of the chain, the chain ends being functionalizedto at least 70 mol % by an amine functional group, preferablycorresponds to the following formula (I):

in which:

-   -   the symbol E denotes a diene elastomer functionalized to at        least 70 mol % at the chain end by an amine functional group,    -   R₁ denotes, as a function of the degree of hydrolysis, a        hydrogen atom or a linear or branched C₁-C₁₀, preferably C₁-C₈,        alkyl radical, more preferably a C₁-C₄ alkyl group, more        preferably a hydrogen atom or an ethyl or methyl radical;    -   R₂ is a saturated or unsaturated, cyclic or non-cyclic, divalent        C₁-C₁₈ aliphatic hydrocarbon group or C₆-C₁₈ aromatic        hydrocarbon group, preferably a saturated, linear or branched,        divalent C₁-C₁₀, indeed even C₁-C₆, aliphatic hydrocarbon group,        more preferably a saturated linear divalent C₃ aliphatic        hydrocarbon group;    -   R₃ and R₄, which are identical or different, represent a linear        or branched C₁-C₁₈, preferably C₁-C₁₀ and more preferably C₁-C₄        alkyl radical, in particular a methyl or ethyl radical, more        preferably a methyl radical, or else R₃ and R₄ form, with N to        which they are bonded, a heterocycle comprising a nitrogen atom        and at least one carbon atom, preferably from 2 to 6 carbon        atoms.

The various aspects, preferred or non-preferred, which precede can becombined with one another.

According to advantageous alternative forms of the invention, at leastone of the three following characteristics is observed and preferablythe three:

-   -   the R₃ and R₄ groups are identical and are methyl or ethyl        groups, preferably methyl groups,    -   the R₂ group is a saturated, linear or branched, divalent C₁-C₆        aliphatic hydrocarbon group, more preferably still a saturated        linear divalent C₃ aliphatic hydrocarbon group,    -   the R₁ group is a hydrogen atom or a linear C₁-C₄ alkyl group,        preferably a methyl or ethyl group; more preferably, R₁ is a        hydrogen atom.

According to a preferred embodiment, the modified diene elastomeraccording to the invention comprises at least 50% by weight, morepreferably at least 70% by weight, with respect to the modified dieneelastomer, of entity functionalized in the middle of the chain by thealkoxysilane group, optionally partially or completely hydrolysed togive silanol, bearing a tertiary amine functional group andfunctionalized to at least 70 mol % at the chain end by an aminefunctional group.

According to another embodiment, which can be combined with thepreceding one, the diene entity functionalized in the middle of thechain by the alkoxysilane group, optionally partially or completelyhydrolysed to give silanol, bearing a tertiary amine functional group,is functionalized to 100% at the chain end by an amine functional group.

The modified diene elastomer according to an embodiment of the inventioncan be prepared according to a process including the modification of theelastomer by reaction of a living diene elastomer with an appropriatefunctionalization agent, that is to say any at least difunctionalmolecule, for the purpose of coupling, the functional group being anytype of chemical group known by a person skilled in the art to reactwith a living chain end. Such a process also forms the subject-matteraccording to an embodiment of the invention.

Thus, according to an embodiment of the invention, the modified dieneelastomer is obtained by the use of the following stages:

-   -   anionic polymerization of at least one conjugated diene monomer        in the presence of a polymerization initiator having an amine        functional group,    -   modification of the living diene elastomer bearing an active        site obtained in the preceding stage by a functionalization        agent, capable of coupling the elastomer chains, bearing at        least one tertiary amine functional group and an alkoxysilane        functional group, which can or cannot be hydrolysed to give        silanol, with a molar ratio of the functionalization agent to        the polymerization initiator with a value ranging from 0.35 to        0.65.

The polymerization initiators comprising an amine functional groupresult in living chains having an amine group at the non-reactive end ofthe chain.

Mention may preferably be made, as polymerization initiators comprisingan amine functional group, of lithium amides, the products of thereaction of an organolithium compound, preferably an alkyllithiumcompound, and of a non-cyclic or cyclic, preferably cyclic, secondaryamine.

Mention may be made, as secondary amine which can be used to prepare theinitiators, of dimethylamine, diethylamine, dipropylamine,di(n-butyl)amine, di(sec-butyl)amine, dipentylamine, dihexylamine,di(n-octyl)amine, di(2-ethylhexyl)amine, dicyclohexylamine,N-methylbenzylamine, diallylamine, morpholine, piperazine,2,6-dimethylmorpholine, 2,6-dimethylpiperazine, 1-ethylpiperazine,2-methylpiperazine, 1-benzylpiperazine, piperidine,3,3-dimethylpiperidine, 2,6-dimethylpiperidine,1-methyl-4-(methylamino)piperidine, 2,2,6,6-tetramethylpiperidine,pyrrolidine, 2,5-dimethylpyrrolidine, azetidine, hexamethyleneimine,heptamethyleneimine, 5-benzyloxyindole, 3-azaspiro[5.5]undecane,3-azabicyclo[3.2.2]nonane, carbazole, bistrimethylsilylamine,pyrrolidine and hexamethyleneamine.

The secondary amine, when it is cyclic, is preferably chosen frompyrrolidine and hexamethyleneamine.

The alkyllithium compound is preferably ethyllithium, n-butyllithium(n-BuLi), isobutyllithium, and the like.

Preferably, the polymerization initiator comprising an amine functionalgroup is soluble in a hydrocarbon solvent without use of a solvatingagent.

The polymerization initiator comprising an amine functional group is areaction product of an alkyllithium compound and of a secondary amine.Depending on the molar ratio of the alkyllithium compound to thesecondary amine, the product of the reaction can comprise residualalkyllithium compound. Consequently, the polymerization initiator can becomposed of a mixture of lithium amide and residual alkyllithiumcompound. This residual alkyllithium compound results in the formationof living chains not bearing an amine group at the chain end. Accordingto an embodiment of the invention, the polymerization initiator does notcomprise more than 30% of alkyllithium compound. Above this value, thedesired technical effects, in particular the improvement in thecompromise in hysteresis and stiffness properties, are not satisfactory.According to an alternative form of the process, the polymerizationinitiator does not comprise alkyllithium compound.

The polymerization is preferably carried out in the presence of an inerthydrocarbon solvent which can, for example, be an aliphatic or alicyclichydrocarbon, such as pentane, hexane, heptane, isooctane, cyclohexane ormethylcyclohexane, or an aromatic hydrocarbon, such as benzene, tolueneor xylene.

The polymerization can be carried out continuously or batchwise. Thepolymerization is generally carried out at a temperature of between 20°C. and 150° C. and preferably in the vicinity of 30° C. to 110° C.

The diene elastomer can have any microstructure which depends on thepolymerization conditions used. The elastomer can be a block,statistical, sequential, microsequential and the like elastomer and canbe prepared in dispersion or in solution. The microstructure of thiselastomer can be determined by the presence or absence of a modifyingand/or randomizing agent and the amounts of modifying and/or randomizingagent employed.

The second stage of the process according to an embodiment of theinvention consists of the modification of the living diene elastomer,obtained on conclusion of the anionic polymerization stage, according tooperating conditions which promote the coupling reaction of the dieneelastomer with an appropriate functionalization agent. This stageresults in the synthesis of a modified diene elastomer predominantlycomprising the coupled entity.

The reaction for modification of the living diene elastomer, obtained onconclusion of the first stage, can take place at a temperature ofbetween −20° C. and 100° C., by addition to the living polymer chains orvice versa of a non-polymerizable functionalization agent capable offorming an alkoxysilane group, which can or cannot be hydrolysed to givesilanol, bearing a tertiary amine functional group, the silicon atombonding two pieces of the elastomer chain. This non-polymerizablecoupling agent makes it possible in particular to obtain the structuresof formula (I) described above. It is in particular a functionalizationagent bearing at least one alkoxysilane functional group, which can orcannot be hydrolysed to give silanol, and two functional groups whichreact with the living elastomer, each of these two functional groupsbeing directly bonded to the silicon atom, and also a tertiary aminefunctional group.

Thus, according to an alternative form of the process of the invention,the functionalization agent corresponds to the formula:

in which:

-   -   R₂ is a saturated or unsaturated, cyclic or non-cyclic, divalent        C₁-C₁₈ aliphatic hydrocarbon group or C₆-C₁₈ aromatic        hydrocarbon group, preferably a linear or branched divalent        C₁-C₁₀, preferably C₁-C₆, aliphatic hydrocarbon radical, better        still a saturated linear divalent C₃ aliphatic hydrocarbon        group;    -   R₃ and R₄, which are identical or different, represent a linear        or branched C₁-C₁₈, preferably C₁-C₁₀ and more preferably C₁-C₄        alkyl radical, in particular a methyl or ethyl radical, more        preferably a methyl radical, or else R₃ and R₄ form, with N to        which they are bonded, a heterocycle comprising a nitrogen atom        and at least one carbon atom, preferably from 2 to 6 carbon        atoms,    -   the linear or branched R′ radicals, which are identical to or        different from one another, represent a C₁-C₁₀, preferably        C₁-C₈, alkyl group, better still a C₁-C₄ alkyl group, more        preferably a methyl and ethyl group.

Mention may be made, for example, as functionalization agentcorresponding to the formula (II), ofN,N-dialkylaminopropyltrialkoxysilanes.

Preferably, R₃ and R₄ present on the nitrogen atom are linear orbranched and have from 1 to 10 carbon atoms, more preferably from 1 to 4carbon atoms, more preferably methyl and ethyl.

The alkoxy substituents formed by the OR′ group are preferablyhydrolysable.

Preferably, the functionalization agent is chosen from3-(N,N-dimethylaminopropyl)trimethoxysilane,3-(N,N-dimethylaminopropyl)triethoxysilane,3-(N,N-diethylaminopropyl)trimethoxysilane,3-(N,N-diethylaminopropyl)triethoxysilane,3-(N,N-dipropylaminopropyl)trimethoxysilane,3-(N,N-dipropylaminopropyl)triethoxysilane,3-(N,N-dibutylaminopropyl)trimethoxysilane,3-(N,N-dibutylaminopropyl)triethoxysilane,3-(N,N-dipentylaminopropyl)trimethoxysilane,3-(N,N-dipentylaminopropyl)triethoxysilane,3-(N,N-dihexylaminopropyl)trimethoxysilane,3-(N,N-dihexylaminopropyl)triethoxysilane,3-(hexamethyleneiminopropyl)trimethoxysilane or3-(hexamethyleneiminopropyl)triethoxysilane. More preferably still, thefunctionalization agent is 3-(N,N-dimethylaminopropyl)trimethoxysilane.

The mixing of the living diene polymer and the functionalization agentcan be carried out by any appropriate means. The time for reactionbetween the living diene polymer and the coupling agent can be between10 seconds and 2 hours.

The molar ratio of the functionalization agent to the initiator of theliving polymer chains varies from 0.35 to 0.65, preferably from 0.40 to0.60 and more preferably still from 0.45 to 0.55.

The process for the synthesis of the modified diene elastomer accordingto an embodiment of the invention can be continued in a way known per seby the stages of recovery of the modified elastomer.

According to alternative forms of this process, these stages comprise astripping stage for the purpose of recovering the elastomer resultingfrom the prior stages in dry form. This stripping stage can inparticular have the effect of hydrolysing all or a portion of thehydrolysable alkoxysilane functional groups of the modified dieneelastomer in order to convert them into silanol functional groups.

According to other alternative forms of this process, these stagescomprise a specific stage of hydrolysis dedicated to the hydrolysis ofall or a portion of the hydrolysable alkoxysilane functional groups ofthe modified diene elastomer in order to convert them into silanolfunctional groups. This stage of complete or partial hydrolysis can becarried out in a way known per se by addition of an acidic or basiccompound. Such hydrolysis stages are described, for example, in thedocument EP 2 266 819 A 1.

According to yet other alternative forms of the invention, it is alsopossible to provide an additional star branching of the modified dieneelastomer according to an embodiment of the invention. This starbranching is advantageously carried out in order to reduce the raw flowof the elastomer matrix. The process for the preparation of the modifieddiene elastomer according to an embodiment of the invention can then,according to one embodiment, comprise a stage of formation ofstar-branched entities, generally prior to the modification stage. Thisstar-branching stage can be carried out by reaction with astar-branching agent known per se, for example based on tin or onsilicon, or also with the same agent of trialkoxysilane type bearing atertiary amine functional group with a molar ratio of thefunctionalization agent to the polymerization initiator with a value ofless than or equal to 0.33.

The stages of these different alternative forms can be combined with oneanother.

Another subject-matter of the invention is a reinforced rubbercomposition based on at least one reinforcing filler and an elastomermatrix comprising at least one modified diene elastomer as describedabove. It should be understood that the rubber composition can compriseone or more of these modified diene elastomers according to embodimentsof the invention.

The reinforced rubber composition according to an embodiment of theinvention can be provided in the crosslinked state or in thenon-crosslinked, in other words crosslinkable, state.

The modified diene elastomer according to the invention can, accordingto different alternative forms, be used alone in the composition or as ablend with at least one other conventional diene elastomer, whether ornot star-branched, coupled or functionalized. Preferably, this otherdiene elastomer used in the invention is selected from the group ofhighly unsaturated diene elastomers consisting of polybutadienes (BRs),synthetic polyisoprenes (IRs), natural rubber (NR), butadienecopolymers, isoprene copolymers and the mixtures of these elastomers.Such copolymers are more preferably selected from the group consistingof butadiene/styrene copolymers (SBRs), isoprene/butadiene copolymers(BIRs), isoprene/styrene copolymers (SIRs) andisoprene/butadiene/styrene copolymers (SBIRs). It is also possible toenvisage a blend with any synthetic elastomer other than a dieneelastomer, indeed even with any polymer other than an elastomer, forexample a thermoplastic polymer.

It should be noted that the improvement in the properties of thecomposition according to embodiments of the invention will be greater asthe proportion of the elastomer(s) different from the modified dieneelastomers of the invention in this composition becomes lower.

Thus, preferably, the elastomer matrix predominantly comprises themodified diene elastomer according to an embodiment of the invention.

When the conventional elastomer used in blending is natural rubberand/or one or more diene polymers, such as, for example, polybutadienes,polyisoprenes or butadiene/styrene or butadiene/styrene/isoprenecopolymers, this elastomer or these elastomers, modified or unmodified,can then be present at from 1 to 70 parts by weight per 100 parts ofmodified diene elastomer according to an embodiment of the invention.

More preferably, the elastomer matrix is composed solely of the modifieddiene elastomer according to an embodiment of the invention.

The rubber composition of embodiments of the invention comprises,besides at least one elastomer matrix as described above, at least onereinforcing filler.

Use may be made of any type of reinforcing filler known for itsabilities to reinforce a rubber composition which can be used for themanufacture of tire treads, for example carbon black, a reinforcinginorganic filler, such as silica, with which is combined, in a knownway, a coupling agent, or also a mixture of these two types of filler.

All carbon blacks, used individually or in the form of mixtures, inparticular blacks of the HAF, ISAF or SAF type, conventionally used inthe treads of tires (“tire-grade” blacks), are suitable as carbonblacks. Mention will more particularly be made, among the latter, of thereinforcing carbon blacks of the 100, 200 or 300 series (ASTM grades),such as, for example, the N115, N134, N234, N326, N330, N339, N347 orN375 blacks. The carbon blacks might, for example, be alreadyincorporated in the isoprene elastomer in the form of a masterbatch(see, for example, Applications WO 97/36724 or WO 99/16600).

“Reinforcing inorganic filler” should be understood, in the presentpatent application, by definition, as any inorganic or mineral filler,whatever its colour and its origin (natural or synthetic), capable ofreinforcing by itself alone, without means other than an intermediatecoupling agent, a rubber composition intended for the manufacture oftires; such a filler is generally characterized, in a known way, by thepresence of hydroxyl (—OH) groups at its surface.

Mineral fillers of the siliceous type, in particular silica (SiO₂), orof the aluminous type, in particular alumina (Al₂O₃), are suitable inparticular as reinforcing inorganic fillers. The silica used can be anyreinforcing silica known to a person skilled in the art, in particularany precipitated or fumed silica exhibiting a BET specific surface and aCTAB specific surface both of less than 450 m²/g, preferably from 30 to400 m²/g, in particular between 60 and 300 m²/g. Mention will also bemade of mineral fillers of the aluminous type, in particular alumina(Al₂O₃) or aluminium (oxide) hydroxides, or else reinforcing titaniumoxides, for example described in U.S. Pat. No. 6,610,261 and U.S. Pat.No. 6,747,087.

Also suitable as reinforcing fillers are reinforcing fillers of anothernature, in particular carbon black, provided that these reinforcingfillers are covered with a siliceous layer or else comprise, at theirsurface, functional sites, in particular hydroxyl sites, requiring theuse of a coupling agent in order to establish the bond between thefiller and the elastomer. Mention may be made, by way of example, forexample, of carbon blacks for tires, such as described, for example, inpatent documents WO 96/37547 and WO 99/28380.

The physical state under which the reinforcing inorganic filler isprovided is not important, whether it is in the form of a powder, ofmicrobeads, of granules, of beads or any other appropriate densifiedform. Of course, the term “reinforcing inorganic filler” is alsounderstood to mean mixtures of different reinforcing fillers, inparticular of highly dispersible siliceous fillers as described above.

Preferably, the amount of total reinforcing filler (carbon black and/orother reinforcing filler, such as silica) is between 10 and 200 phr,more preferably between 30 and 150 phr and more preferably still between70 and 130 phr, the optimum being, in a known way, different accordingto the specific applications targeted.

According to an alternative form of the invention, the reinforcingfiller is predominantly other than carbon black, that is to say that itcomprises more than 50% by weight, of the total weight of the filler, ofone or more fillers other than carbon black, in particular a reinforcinginorganic filler, such as silica; indeed, it is even exclusivelycomposed of such a filler.

According to this alternative form, when carbon black is also present,it can be used at a content of less than 20 phr, more preferably of lessthan 10 phr (for example, between 0.5 and 20 phr, in particular from 1to 10 phr).

According to another alternative form of the invention, use is made of areinforcing filler predominantly comprising carbon black and optionallysilica or another inorganic filler.

When the reinforcing filler comprises a filler requiring the use of acoupling agent in order to establish the bond between the filler and theelastomer, the rubber composition according to an embodiment of theinvention in addition conventionally comprises an agent capable ofeffectively providing this bond. When silica is present in thecomposition as reinforcing filler, use may be made, as coupling agents,of organosilanes, in particular alkoxysilane polysulphides ormercaptosilanes, or also of at least bifunctional polyorganosiloxanes.

In the composition according to an embodiment the invention, the contentof coupling agent is advantageously less than 20 phr, it beingunderstood that it is generally desirable to use as little as possibleof it. Its content is preferably between 0.5 and 12 phr. The presence ofthe coupling agent depends on the presence of the reinforcing inorganicfiller. Its content is easily adjusted by a person skilled in the artaccording to the content of this filler; it is typically of the order of0.5% to 15% by weight, with respect to the amount of reinforcinginorganic filler other than carbon black.

The rubber composition according to an embodiment of the invention canalso comprise, in addition to the coupling agents, coupling activators,agents for covering the fillers or more generally processing aidscapable, in a known way, by virtue of an improvement in the dispersionof the filler in the rubber matrix and of a lowering of the viscosity ofthe composition, of improving its ability to be processed in the rawstate, these agents being, for example, hydrolysable silanes, such asalkylalkoxysilanes, polyols, polyethers, primary, secondary or tertiaryamines, or hydroxylated or hydrolysable polyorganosiloxanes.

The rubber compositions in accordance with embodiments of the inventioncan also comprise reinforcing organic fillers which can replace all or aportion of the carbon blacks or of the other reinforcing inorganicfillers described above. Mention may be made, as examples of reinforcingorganic fillers, of functionalized polyvinyl organic fillers, such asdescribed in Applications WO-A-2006/069792, WO-A-2006/069793,WO-A-2008/003434 and WO-A-2008/003435.

The rubber composition according to an embodiment of the invention canalso comprise all or a portion of the usual additives generally used inelastomer compositions intended for the manufacture of tires, such as,for example, pigments, non-reinforcing fillers, protective agents, suchas antiozone waxes, chemical antiozonants or antioxidants, antifatigueagents, plasticizing agents, reinforcing or plasticizing resins,methylene acceptors (for example, phenolic novolak resin) or methylenedonors (for example, HMT or H3M), such as described, for example, inApplication WO 02/10269, a crosslinking system based either on sulphuror on sulphur donors and/or on peroxide and/or on bismaleimides,vulcanization accelerators or vulcanization activators.

The composition is manufactured in appropriate mixers, using twosuccessive phases of preparation well known to a person skilled in theart: a first phase of thermomechanical working or kneading(“non-productive” phase) at high temperature, up to a maximumtemperature of between 110° C. and 190° C., preferably between 130° C.and 180° C., followed by a second phase of mechanical working(“productive” phase) down to a lower temperature, typically of less than110° C., for example between 40° C. and 100° C., during which finishingphase the crosslinking system is incorporated.

The process for the preparation of a composition according to anembodiment of the invention generally comprises:

(i) the implementation, at a maximum temperature of between 130° C. and200° C., of a first step of thermomechanical working of the constituentsof the composition comprising the modified diene elastomer according toan embodiment of the invention and a reinforcing filler, with theexception of a crosslinking system, then

(ii) the implementation, at a temperature lower than said maximumtemperature of said first step, of a second step of mechanical workingduring which said crosslinking system is incorporated.

This process can also comprise, prior to the implementation of theabovementioned stages (i) and (ii), the stages of the preparation of thediene elastomer predominantly coupled by an alkoxysilane group bearing atertiary amine functional group and bonded to the diene elastomer viathe silicon atom according to the process described above.

Another subject-matter of the invention is a semi-finished article madeof rubber for a tire, comprising a rubber composition according to anembodiment of the invention which is crosslinkable or crosslinked orcomposed of such a composition.

The final composition thus obtained can subsequently be calendered, forexample in the form of a sheet or a plaque or also extruded, for examplein order to form a rubber profiled element which can be used as asemi-finished rubber product intended for the tire. Such a semi-finishedproduct also forms the subject-matter of an embodiment of the invention.

Due to the improvement in the hysteresis/raw processing/stiffnesscompromise which characterizes a reinforced rubber composition accordingto an embodiment of the invention, it should be noted that such acomposition can constitute any semi-finished product of the tire andvery particularly the tread, reducing in particular its rollingresistance and improving the wear resistance.

A final subject-matter of an embodiment of the invention is thus a tirecomprising a semi-finished article according to the invention, inparticular a tread.

The abovementioned characteristics of the embodiments of the presentinvention, and also others, will be better understood on reading thefollowing description of several implementational example embodiments ofthe invention, given by way of illustration and without limitation.

EXAMPLES Examples of the Preparation of Modified Elastomers

Preparation of the Polymer A: SBR Non-Functional—Control

1.8 kg of styrene and 4.9 kg of butadiene, and also 395 ml of a 0.1mol·l⁻¹ solution of tetrahydrofurfuryl ether in methylcyclohexane, areinjected into a 90-liter reactor, maintained under a nitrogen pressureof approximately 2 bar, containing 44.7 kg of methylcyclohexane. Afterneutralization of the impurities in the solution to be polymerized byaddition of n-butyllithium, 535 ml of 0.05 mol·l⁻¹ n-butyllithium inmethylcyclohexane are added. The polymerization is carried out at 50° C.

After 40 minutes, the degree of conversion of the monomers reaches 90%.This content is determined by weighing an extract dried at 140° C. undera reduced pressure of 200 mmHg. 530 ml of a 0.15 mol·l⁻¹ solution ofmethanol in toluene are then added. The solution is subsequentlyantioxidized by addition of 0.8 part per hundred parts of elastomer(phr) of 4,4′-methylenebis(2,6-(tert-butyl)phenol) and 0.2 part perhundred parts of elastomer (phr) ofN-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine. The copolymer thustreated is separated from its solution by a steam stripping operationand then dried on open mills at 100° C. for 15 minutes.

The Mooney viscosity of the polymer is 60.

The number-average molar mass M_(n) of this copolymer, determined by theSEC technique, is 192 000 g·mol⁻¹ and the polydispersity index PI is1.07.

The microstructure of this copolymer is determined by the NIR method.The content of 1,2-units is 59%, with respect to the butadiene units.The content by weight of styrene is 25%.

The glass transition temperature of this copolymer is −24° C.

Preparation of the Polymer B: SBR Amine-Functional at the ChainEnd—Control

1.8 kg of styrene and 4.9 kg of butadiene, and also 395 ml of a 0.1mol·l⁻¹ solution of tetrahydrofurfuryl ether in methylcyclohexane, areinjected into a 90-liter reactor, maintained under a nitrogen pressureof approximately 2 bar, containing 44.7 kg of methylcyclohexane. Afterneutralization of the impurities in the solution to be polymerized byaddition of n-butyllithium, 1.07 l of 0.05 mol·l⁻¹ lithiumhexamethyleneamine in methylcyclohexane are added. The polymerization iscarried out at 50° C.

After 32 minutes, the degree of conversion of the monomers reaches 90%.This content is determined by weighing an extract dried at 140° C. undera reduced pressure of 200 mmHg. A control sample is then withdrawn fromthe reactor and then stopped with an excess of methanol with respect tothe lithium. The intrinsic viscosity (“initial” viscosity), which ismeasured at 0.1 g·l⁻¹ in toluene at 25° C., is 1.10 dl·g⁻¹. 268 ml of a0.1 mol·l⁻¹ solution of dimethyldichlorosilane in methylcyclohexane areadded. After reacting at 50° C. for 20 minutes, the solution isantioxidized by addition of 0.8 part per hundred parts of elastomer(phr) of 4,4′-methylenebis(2,6-(tert-butyl)phenol) and 0.2 part perhundred parts of elastomer (phr) ofN-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine. The copolymer thustreated is separated from its solution by a steam stripping operationand then dried on open mills at 100° C. for 15 minutes.

The “final” intrinsic viscosity measured is 1.80 dl·g⁻¹. The jump inviscosity, defined as the ratio of said “final” viscosity to said“initial” viscosity, is in this instance 1.63. The Mooney viscosity ofthe polymer thus coupled is 59.

The number-average molar mass M_(n) of this copolymer, determined by theSEC technique, is 188 000 g·mol⁻¹ and the polydispersity index PI is1.09.

The microstructure of this copolymer is determined by the NIR method.The content of 1,2-units is 60%, with respect to the butadiene units.The content by weight of styrene is 25%.

The glass transition temperature of this copolymer is −24° C.

Preparation of the Polymer C: SBR Aminoalkoxysilane-Functional in theMiddle of the Chain—Control

1.8 kg of styrene and 4.9 kg of butadiene, and also 395 ml of a 0.1mol·l⁻¹ solution of tetrahydrofurfuryl ether in methylcyclohexane, areinjected into a 90-liter reactor, maintained under a nitrogen pressureof approximately 2 bar, containing 44.7 kg of methylcyclohexane. Afterneutralization of the impurities in the solution to be polymerized byaddition of n-butyllithium, 1.07 l of 0.05 mol·l⁻¹ n-butyllithium inmethylcyclohexane are added. The polymerization is carried out at 50° C.

After 30 minutes, the degree of conversion of the monomers reaches 90%.This content is determined by weighing an extract dried at 140° C. undera reduced pressure of 200 mmHg. A control sample is then withdrawn fromthe reactor and then stopped with an excess of methanol with respect tothe lithium. The intrinsic viscosity (“initial” viscosity), which ismeasured at 0.1 g·dl⁻¹ in toluene at 25° C., is 1.11 dl·g⁻¹. 268 ml of a0.1 mol·l⁻¹ solution of 3-(N,N-dimethylaminopropyl)trimethoxysilane inmethylcyclohexane are added. After reacting at 50° C. for 20 minutes,the solution is subsequently antioxidized by addition of 0.8 part perhundred parts of elastomer (phr) of4,4′-methylenebis(2,6-(tert-butyl)phenol) and 0.2 part per hundred partsof elastomer (phr) ofN-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine. The copolymer thustreated is separated from its solution by a steam stripping operationand then dried on open mills at 100° C. for 15 minutes.

The “final” intrinsic viscosity measured is 1.78 dl·g⁻¹. The jump inviscosity, defined as the ratio of said “final” viscosity to said“initial” viscosity, is in this instance 1.60. The Mooney viscosity ofthe polymer thus coupled is 59.

The number-average molar mass M_(n) of this copolymer, determined by theSEC technique, is 187 000 g·mol⁻¹ and the polydispersity index PI is1.13.

The percentage by weight of coupled entities, determined by the highresolution SEC technique, is 85%.

The microstructure of this copolymer is determined by the NIR method.The content of 1,2-units is 60%, with respect to the butadiene units.The content by weight of styrene is 25%.

The glass transition temperature of this copolymer is −24° C.

The content of residual SiOCH₃ functional group after stripping/drying,determined by ¹H NMR, is 65%.

Preparation of the Polymer D: SBR Silanol-Functional in the Middle ofthe Chain—Control

1.8 kg of styrene and 4.9 kg of butadiene, and also 395 ml of a 0.1mol·l⁻¹ solution of tetrahydrofurfuryl ether in methylcyclohexane, areinjected into a 90-liter reactor, maintained under a nitrogen pressureof approximately 2 bar, containing 44.7 kg of methylcyclohexane. Afterneutralization of the impurities in the solution to be polymerized byaddition of n-butyllithium, 1.07 l of 0.05 mol·l⁻¹ n-butyllithium inmethylcyclohexane are added. The polymerization is carried out at 50° C.

After 30 minutes, the degree of conversion of the monomers reaches 90%.This content is determined by weighing an extract dried at 140° C. undera reduced pressure of 200 mmHg. A control sample is then withdrawn fromthe reactor and then stopped with an excess of methanol with respect tothe lithium. The intrinsic viscosity (“initial” viscosity), which ismeasured at 0.1 g·l⁻¹ in toluene at 25° C., is 1.10 dl·g⁻¹. 268 ml of a0.1 mol·l⁻¹ solution of methyltrichlorosilane in methylcyclohexane areadded. After reacting at 0° C. for 20 minutes, an excess of water isadded in order to hydrolyse the SiCl functional groups present on thepolymer chains. The solution is subsequently antioxidized by addition of0.8 part per hundred parts of elastomer (phr) of4,4′-methylenebis(2,6-di(tert-butyl)phenol) and 0.2 part per hundredparts of elastomer (phr) ofN-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine. The copolymer thustreated is separated from its solution by a steam stripping operationand then dried on open mills at 100° C. for 15 minutes.

The “final” intrinsic viscosity measured is 1.80 dl·g⁻¹. The jump inviscosity, defined as the ratio of said “final” viscosity to said“initial” viscosity, is in this instance 1.64. The Mooney viscosity ofthe polymer thus coupled is 60.

The number-average molar mass M_(n) of this copolymer, determined by theSEC technique, is 190 000 g·mol⁻¹ and the polydispersity index PI is1.10.

The percentage by weight of coupled entities, determined by the highresolution SEC technique, is 82%.

The microstructure of this copolymer is determined by the NIR method.The content of 1,2-units is 60%, with respect to the butadiene units.The content by weight of styrene is 25%.

The glass transition temperature of this copolymer is −24° C.

Preparation of the Polymer E: SBR Epoxide+Alkoxysilane-Functional in theMiddle of the Chain—Control

1.8 kg of styrene and 4.9 kg of butadiene, and also 395 ml of a 0.1mol·l⁻¹ solution of tetrahydrofurfuryl ether in methylcyclohexane, areinjected into a 90-liter reactor, maintained under a nitrogen pressureof approximately 2 bar, containing 44.7 kg of methylcyclohexane. Afterneutralization of the impurities in the solution to be polymerized byaddition of n-butyllithium, 1.07 l of 0.05 mol·l⁻¹ n-butyllithium inmethylcyclohexane are added. The polymerization is carried out at 50° C.

After 30 minutes, the degree of conversion of the monomers reaches 90%.This content is determined by weighing an extract dried at 140° C. undera reduced pressure of 200 mmHg. A control sample is then withdrawn fromthe reactor and then stopped with an excess of methanol with respect tothe lithium. The intrinsic viscosity (“initial” viscosity), which ismeasured at 0.1 g·dl⁻¹ in toluene at 25° C., is 1.10 dl·g⁻¹. 268 ml of a0.1 mol·l⁻¹ solution of 3-(glycidyloxypropyl)trimethoxysilane inmethylcyclohexane are added. After reacting at 50° C. for 20 minutes,the solution is subsequently antioxidized by addition of 0.8 part perhundred parts of elastomer (phr) of4,4′-methylenebis(2,6-(tert-butyl)phenol) and 0.2 part per hundred partsof elastomer (phr) ofN-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine. The copolymer thustreated is separated from its solution by a steam stripping operationand then dried on open mills at 100° C. for 15 minutes.

The “final” intrinsic viscosity measured is 1.77 dl·g⁻¹. The jump inviscosity, defined as the ratio of said “final” viscosity to said“initial” viscosity, is in this instance 1.61. The Mooney viscosity ofthe polymer thus coupled is 58.

The number-average molar mass M_(n) of this copolymer, determined by theSEC technique, is 186 000 g·mol⁻¹ and the polydispersity index PI is1.14.

The percentage by weight of coupled entities, determined by the highresolution SEC technique, is 86%.

The microstructure of this copolymer is determined by the NIR method.The content of 1,2-units is 60%, with respect to the butadiene units.The content by weight of styrene is 25%.

The glass transition temperature of this copolymer is −24° C.

Preparation of the Polymer F: SBR Silanol+Polyether-Functional in theMiddle of the Chain—Control

1.8 kg of styrene and 4.9 kg of butadiene, and also 395 ml of a 0.1mol·l⁻¹ solution of tetrahydrofurfuryl ether in methylcyclohexane, areinjected into a 90-liter reactor, maintained under a nitrogen pressureof approximately 2 bar, containing 44.7 kg of methylcyclohexane. Afterneutralization of the impurities in the solution to be polymerized byaddition of n-butyllithium, 1.07 l of 0.05 mol·l⁻¹ n-butyllithium inmethylcyclohexane are added. The polymerization is carried out at 50° C.

After 30 minutes, the degree of conversion of the monomers reaches 90%.This content is determined by weighing an extract dried at 140° C. undera reduced pressure of 200 mmHg. A control sample is then withdrawn fromthe reactor and then stopped with an excess of methanol with respect tothe lithium. The intrinsic viscosity (“initial” viscosity), which ismeasured at 0.1 g·dl⁻¹ in toluene at 25° C., is 1.10 dl·g⁻¹. 268 ml of a0.1 mol·l⁻¹ solution of poly(oxy-1,2-ethanediyl),α-[3-(dichloromethylsilyl)propyl]-ω-[3-(dichloromethylsilyl)propoxy], indiethyl ether are added. After reacting at 50° C. for 90 minutes, anexcess of water is added in order to neutralize the SiCl functionalgroups present on the polymer chains. The solution is subsequentlyantioxidized by addition of 0.8 part per hundred parts of elastomer(phr) of 4,4′-methylenebis(2,6-(tert-butyl)phenol) and 0.2 part perhundred parts of elastomer (phr) ofN-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine. The copolymer thustreated is separated from its solution by a steam stripping operationand then dried on open mills at 100° C. for 15 minutes.

The “final” intrinsic viscosity measured is 1.76 dl·g⁻¹. The jump inviscosity, defined as the ratio of said “final” viscosity to said“initial” viscosity, is in this instance 1.60. The Mooney viscosity ofthe polymer thus coupled is 59.

The number-average molar mass M_(n) of this copolymer, determined by theSEC technique, is 186 000 g·mol⁻¹ and the polydispersity index PI is1.15.

The microstructure of this copolymer is determined by the NIR method.The content of 1,2-units is 60%, with respect to the butadiene units.The content by weight of styrene is 25%.

The glass transition temperature of this copolymer is −24° C.

Preparation of the Polymer G: SBR Silanol-Functional at the ChainEnd—Control

1.8 kg of styrene and 4.9 kg of butadiene, and also 395 ml of a 0.1mol·l⁻¹ solution of tetrahydrofurfuryl ether in methylcyclohexane, areinjected into a 90-liter reactor, maintained under a nitrogen pressureof approximately 2 bar, containing 44.7 kg of methylcyclohexane. Afterneutralization of the impurities in the solution to be polymerized byaddition of n-butyllithium, 535 ml of 0.05 mol·l⁻¹ n-butyllithium inmethylcyclohexane are added. The polymerization is carried out at 50° C.

After 40 minutes, the degree of conversion of the monomers reaches 90%.This content is determined by weighing an extract dried at 140° C. undera reduced pressure of 200 mmHg. 134 ml of a 0.1 mol·l⁻¹ solution ofhexamethylcyclotrisiloxane in methylcyclohexane are then added. After 30minutes at 60° C., 535 ml of a 0.15 mol·l⁻¹ solution of methanol intoluene are then added. The solution is subsequently antioxidized byaddition of 0.8 part per hundred parts of elastomer (phr) of4,4′-methylenebis(2,6-(tert-butyl)phenol) and 0.2 part per hundred partsof elastomer (phr) ofN-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine. The copolymer thustreated is separated from its solution by a steam stripping operationand then dried on open mills at 100° C. for 15 minutes.

The Mooney viscosity of the polymer is 59.

The number-average molar mass M_(n) of this copolymer, determined by theSEC technique, is 190 000 g·mol⁻¹ and the polydispersity index PI is1.05.

The microstructure of this copolymer is determined by the NIR method.The content of 1,2-units is 59%, with respect to the butadiene units.The content by weight of styrene is 25%.

The glass transition temperature of this copolymer is −24° C.

Preparation of the Polymer H: SBR Amine-Functional at the Chain End andAminoalkoxysilane-Functional in the Middle of the Chain(Functionalization Agent: Dimethylaminopropyltrimethoxysilane) Accordingto an Embodiment of the Invention

1.8 kg of styrene and 4.9 kg of butadiene, and also 395 ml of a 0.1mol·l⁻¹ solution of tetrahydrofurfuryl ether in methylcyclohexane, areinjected into a 90-liter reactor, maintained under a nitrogen pressureof approximately 2 bar, containing 44.7 kg of methylcyclohexane. Afterneutralization of the impurities in the solution to be polymerized byaddition of n-butyllithium, 1.07 l of 0.05 mol·l⁻¹ lithiumhexamethyleneamine in methylcyclohexane are added. The polymerization iscarried out at 50° C.

After 32 minutes, the degree of conversion of the monomers reaches 90%.This content is determined by weighing an extract dried at 140° C. undera reduced pressure of 200 mmHg. A control sample is then withdrawn fromthe reactor and then stopped with an excess of methanol with respect tothe lithium. The intrinsic viscosity (“initial” viscosity), which ismeasured at 0.1 g·dl⁻¹ in toluene at 25° C., is 1.10 dl·g⁻¹. 268 ml of a0.1 mol·l⁻¹ solution of 3-(N,N-dimethylaminopropyl)trimethoxysilane inmethylcyclohexane are added. After reacting at 50° C. for 20 minutes,the solution is subsequently antioxidized by addition of 0.8 part perhundred parts of elastomer (phr) of4,4′-methylenebis(2,6-(tert-butyl)phenol) and 0.2 part per hundred partsof elastomer (phr) ofN-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine. The copolymer thustreated is separated from its solution by a steam stripping operationand then dried on open mills at 100° C. for 15 minutes.

The “final” intrinsic viscosity measured is 1.79 dl·g⁻¹. The jump inviscosity, defined as the ratio of said “final” viscosity to said“initial” viscosity, is in this instance 1.63. The Mooney viscosity ofthe polymer thus coupled is 59.

The number-average molar mass M_(n) of this copolymer, determined by theSEC technique, is 189 000 g·mol⁻¹ and the polydispersity index PI is1.13.

The percentage by weight of coupled entities, determined by the highresolution SEC technique, is 79%.

The microstructure of this copolymer is determined by the NIR method.The content of 1,2-units is 60%, with respect to the butadiene units.The content by weight of styrene is 25%.

The glass transition temperature of this copolymer is −24° C.

The content of residual SiOCH₃ functional group after stripping/drying,determined by ¹H NMR, is 45%.

Preparation of the Polymer I: SBR Amine-Functional at the Chain End andAminoalkoxysilane-Functional in the Middle of the Chain(Functionalization Agent: Diethylaminopropyltrimethoxysilane) Accordingto an Embodiment of the Invention

1.8 kg of styrene and 4.9 kg of butadiene, and also 395 ml of a 0.1mol·l⁻¹ solution of tetrahydrofurfuryl ether in methylcyclohexane, areinjected into a 90-liter reactor, maintained under a nitrogen pressureof approximately 2 bar, containing 44.7 kg of methylcyclohexane. Afterneutralization of the impurities in the solution to be polymerized byaddition of n-butyllithium, 1.07 l of 0.05 mol·l⁻¹ lithiumhexamethyleneamine in methylcyclohexane are added. The polymerization iscarried out at 50° C.

After 32 minutes, the degree of conversion of the monomers reaches 90%.This content is determined by weighing an extract dried at 140° C. undera reduced pressure of 200 mmHg. A control sample is then withdrawn fromthe reactor and then stopped with an excess of methanol with respect tothe lithium. The intrinsic viscosity (“initial” viscosity), which ismeasured at 0.1 g·dl⁻¹ in toluene at 25° C., is 1.12 dl·g⁻¹. 268 ml of a0.1 mol·l⁻¹ solution of 3-(N,N-diethylaminopropyl)trimethoxysilane inmethylcyclohexane are added. After reacting at 50° C. for 20 minutes,the solution is subsequently antioxidized by addition of 0.8 part perhundred parts of elastomer (phr) of4,4′-methylenebis(2,6-(tert-butyl)phenol) and 0.2 part per hundred partsof elastomer (phr) ofN-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine. The copolymer thustreated is separated from its solution by a steam stripping operationand then dried on open mills at 100° C. for 15 minutes.

The “final” intrinsic viscosity measured is 1.80 dl·g⁻¹. The jump inviscosity, defined as the ratio of said “final” viscosity to said“initial” viscosity, is in this instance 1.61. The Mooney viscosity ofthe polymer thus coupled is 61.

The number-average molar mass M_(n) of this copolymer, determined by theSEC technique, is 192 000 g·mol⁻¹ and the polydispersity index PI is1.14.

The percentage by weight of coupled entities, determined by the highresolution SEC technique, is 81%.

The microstructure of this copolymer is determined by the NIR method.The content of 1,2-units is 60%, with respect to the butadiene units.The content by weight of styrene is 25%.

The glass transition temperature of this copolymer is −24° C.

The content of residual SiOCH₃ functional group after stripping/drying,determined by ¹H NMR, is 65%.

Preparation of the Polymer J: SBR Amine-Functional at the Chain End andAminoalkoxysilane-Functional in the Middle of the Chain(Functionalization Agent: Dimethylaminopropyltrimethoxysilane),Hydrolysed, According to an Embodiment of the Invention

1.8 kg of styrene and 4.9 kg of butadiene, and also 395 ml of a 0.1mol·l⁻¹ solution of tetrahydrofurfuryl ether in methylcyclohexane, areinjected into a 90-liter reactor, maintained under a nitrogen pressureof approximately 2 bar, containing 44.7 kg of methylcyclohexane. Afterneutralization of the impurities in the solution to be polymerized byaddition of n-butyllithium, 1.07 l of 0.05 mol·l⁻¹ lithiumhexamethyleneamine in methylcyclohexane are added. The polymerization iscarried out at 50° C.

After 32 minutes, the degree of conversion of the monomers reaches 90%.This content is determined by weighing an extract dried at 140° C. undera reduced pressure of 200 mmHg. A control sample is then withdrawn fromthe reactor and then stopped with an excess of methanol with respect tothe lithium. The intrinsic viscosity (“initial” viscosity), which ismeasured at 0.1 g·dl⁻¹ in toluene at 25° C., is 1.10 dl·g⁻¹. 268 ml of a0.1 mol·l⁻¹ solution of 3-(N,N-dimethylaminopropyl)trimethoxysilane inmethylcyclohexane are added. After reacting at 50° C. for 20 minutes, a0.1 mol·l⁻¹ aqueous hydrochloric acid solution (2 mol. Eq. of HCl withrespect to the lithium) is added and the solution is stirred for 30minutes. The solution is subsequently antioxidized by addition of 0.8part per hundred parts of elastomer (phr) of4,4′-methylenebis(2,6-(tert-butyl)phenol) and 0.2 part per hundred partsof elastomer (phr) ofN-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine. The copolymer thustreated is separated from its solution by a steam stripping operationand then dried on open mills at 100° C. for 15 minutes.

The “final” intrinsic viscosity measured is 1.79 dl·g⁻¹. The jump inviscosity, defined as the ratio of said “final” viscosity to said“initial” viscosity, is in this instance 1.63. The Mooney viscosity ofthe polymer thus coupled is 61.

The number-average molar mass M_(n) of this copolymer, determined by theSEC technique, is 190 000 g·mol⁻¹ and the polydispersity index PI is1.15.

The percentage by weight of coupled entities, determined by the highresolution SEC technique, is 81%.

The microstructure of this copolymer is determined by the NIR method.The content of 1,2-units is 60%, with respect to the butadiene units.The content by weight of styrene is 25%.

The glass transition temperature of this copolymer is −24° C.

The content of residual SiOCH₃ functional group afterhydrolysis/stripping/drying, determined by ¹H NMR, is zero.

Comparative Examples of Rubber Compositions

Measurements and Tests Used

Size Exclusion Chromatography

The SEC (Size Exclusion Chromatography) technique makes it possible toseparate macromolecules in solution according to their size throughcolumns filled with a porous gel. The macromolecules are separatedaccording to their hydrodynamic volume, the bulkiest being eluted first.

Without being an absolute method, SEC makes it possible to comprehendthe distribution of the molar masses of a polymer. The variousnumber-average molar masses (Mn) and weight-average molar masses (Mw)can be determined from commercial standards and the polydispersity index(PI=Mw/Mn) can be calculated via a “Moore” calibration.

There is no specific treatment of the polymer sample before analysis.The latter is simply dissolved in the elution solvent at a concentrationof approximately 1 g·l⁻¹. The solution is then filtered through a filterwith a porosity of 0.45 μm before injection.

The apparatus used is a “Waters Alliance” chromatographic line. Theelution solvent is either tetrahydrofuran or tetrahydrofuran+1 vol % ofdiisopropylamine+1 vol % of triethylamine, the flow rate is 1 ml·min⁻¹,the temperature of the system is 35° C. and the analytical time is 30min. A set of two Waters columns with the “Styragel HT6E” trade name isused. The volume of the solution of the polymer sample injected is 100The detector is a “Waters 2410” differential refractometer and thesoftware for making use of the chromatographic data is the “WatersEmpower” system.

The calculated average molar masses are relative to a calibration curveproduced for SBRs having the following microstructure: 25% by weight ofunits of styrene type, 23% by weight of units of 1,2-type and 50% byweight of units of trans-1,4-type.

High-Resolution Size Exclusion Chromatography

The high-resolution SEC technique is used to determine the percentagesby weight of the various populations of chains present in a polymersample.

There is no specific treatment of the polymer sample before analysis.The latter is simply dissolved in the elution solvent at a concentrationof approximately 1 g·l⁻¹. The solution is then filtered through a filterwith a porosity of 0.45 μm before injection.

The apparatus used is a “Waters Alliance 2695” chromatographic line. Theelution solvent is tetrahydrofuran, the flow rate is 0.2 ml·min⁻¹ andthe temperature of the system is 35° C. A set of three identical columnsin series is used (Shodex, length 300 mm, diameter 8 mm). The number oftheoretical plates of the set of columns is greater than 22 000. Thevolume of the solution of the polymer sample injected is 50 μl. Thedetector is a “Waters 2414” differential refractometer and the softwarefor making use of the chromatographic data is the “Waters Empower”system.

The calculated molar masses are relative to a calibration curve producedfor SBRs having the following microstructure: 25% by weight of units ofstyrene type, 23% by weight of units of 1,2-type and 50% by weight ofunits of trans-1,4-type.

Mooney Viscosity

For the polymers and rubber compositions, the Mooney viscosities ML₍₁₊₄₎100° C. are measured according to Standard ASTM D-1646.

Use is made of an oscillating consistometer as described in StandardASTM D-1646. The Mooney plasticity measurement is carried out accordingto the following principle: the composition in the raw state (i.e.,before curing) is moulded in a cylindrical chamber heated to 100° C.After preheating for one minute, the rotor rotates within the testspecimen at 2 revolutions/minute and the working torque for maintainingthis movement after rotating for 4 minutes is measured. The Mooneyplasticity ML₍₁₊₄₎ is expressed in “Mooney unit” (MU, with 1 MU=0.83N·m).

Differential Calorimetry

The glass transition temperatures (Tg) of the elastomers are determinedusing a differential scanning calorimeter.

Near-Infrared (NIR) Spectroscopy

The microstructure of the elastomers is characterized by thenear-infrared (NIR) spectroscopy technique.

Near-infrared spectroscopy (NIR) is used to quantitatively determine thecontent by weight of styrene in the elastomer and also itsmicrostructure (relative distribution of the 1,2-, trans-1,4- andcis-1,4-butadiene units). The principle of the method is based on theBeer-Lambert law generalized for a multicomponent system. As the methodis indirect, it involves a multivariate calibration [Vilmin, F., Dussap,C. and Coste, N., Applied Spectroscopy, 2006, 60, 619-29] carried outusing standard elastomers having a composition determined by ¹³C NMR.The styrene content and the microstructure are then calculated from theNIR spectrum of an elastomer film having a thickness of approximately730 μm. The spectrum is acquired in transmission mode between 4000 and6200 cm⁻¹ with a resolution of 2 cm⁻¹ using a Bruker Tensor 37Fourier-transform near-infrared spectrometer equipped with an InGaAsdetector cooled by the Peltier effect.

Proton Nuclear Magnetic Resonance (¹H NMR)

The content of SiOCH₃ functional group is determined by ¹H NMR. The NMRanalyses are carried out on a Bruker 500 MHz spectrometer equipped witha 5 mm BBIz “broad band” probe. For the quantitative ¹H NMR experiment,the sequence uses a 30° pulse and a repetition time of 2 seconds. Thesamples are dissolved in carbon disulphide (CS₂). 100 μl of deuteratedcyclohexane (C₆D₁₂) are added for the lock signal.

Intrinsic Viscosity

The intrinsic viscosity of the elastomers at 25° C. is determined from a0.1 g·dl⁻¹ solution of elastomer in toluene, according to the followingprinciple:

The intrinsic viscosity is determined by the measurement of the flowtime t of the polymer solution and of the flow time t_(o) of the toluenein a capillary tube.

The flow time of the toluene and the flow time of the 0.1 g·dl⁻¹ polymersolution are measured in an Ubbelohde tube (diameter of the capillary0.46 mm, capacity from 18 to 22 ml) placed in a bath thermostaticallycontrolled at 25±0.1° C.

The intrinsic viscosity is obtained by the following relationship:

$\eta_{inh} = {\frac{1}{C}{\ln\left\lbrack \frac{(t)}{\left( t_{o} \right)} \right\rbrack}}$

with:

-   -   C: concentration of the solution of polymer in toluene in        g·dl⁻¹,    -   t: flow time of the solution of polymer in toluene in seconds,    -   t_(o): flow time of the toluene in seconds,    -   η_(inh): intrinsic viscosity, expressed in dl·g⁻¹.

Dynamic Properties

The dynamic properties G* and tan(δ) max are measured on a viscosityanalyser (Metravib VA4000) according to Standard ASTM D 5992-96. Theresponse of a sample of vulcanized composition (cylindrical testspecimen with a thickness of 2 mm and a cross-section of 79 mm²),subjected to a simple alternating sinusoidal shear stress, at afrequency of 10 Hz, under standard temperature conditions (40° C.)according to Standard ASTM D 1349-99, is recorded. A strain amplitudesweep is carried out from 0.1% to 50% peak-to-peak (outward cycle) andthen from 50% to 0.1% peak-to-peak (return cycle). The results made useof are the complex dynamic shear modulus (G*) and the loss factortan(δ). For the return cycle, the maximum value of tan(δ) observed,denoted tan(δ) max, is indicated. This value is representative of thehysteresis of the material and in the present case of the rollingresistance: the smaller the value of tan(δ) max, the lower the rollingresistance. The G* values, measured at 40° C., are representative of thestiffness, that is to say of the resistance to deformation: the higherthe value of G*, the greater the stiffness of the material and thus thehigher the wear resistance.

The Compositions

Ten compositions given in Table 1 below are compared. Seven of them(compositions 4 to 10) are not in accordance with regard to thecomposition recommended by an embodiment of the invention. Theformulations are expressed in percentage by weight per 100 parts byweight of elastomer (phr).

TABLE 1 Examples Comparative examples 1 2 3 4 5 6 7 8 9 10 Polymer A 100Polymer B 100 Polymer C 100 Polymer D 100 Polymer E 100 Polymer F 100Polymer G 100 Polymer H 100 Polymer I 100 Polymer J 100 Silica (1) 80 8080 80 80 80 80 80 80 80 N234 1 1 1 1 1 1 1 1 1 1 MES Oil (2) 15 15 15 1515 15 15 15 15 15 Resin (3) 15 15 15 15 15 15 15 15 15 15 Coupling agent(4) 6.4 6.4 6.4 6.4 6.4 6.4 6.4 6.4 6.4 6.4 ZnO 2.5 2.5 2.5 2.5 2.5 2.52.5 2.5 2.5 2.5 Stearic acid 2 2 2 2 2 2 2 2 2 2 Antioxidant (5) 1.9 1.91.9 1.9 1.9 1.9 1.9 1.9 1.9 1.9 Antiozone wax 1.5 1.5 1.5 1.5 1.5 1.51.5 1.5 1.5 1.5 C32ST (6) Diphenylguanidine 1.5 1.5 1.5 1.5 1.5 1.5 1.51.5 1.5 1.5 Sulphur 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 Sulphenamide(7) 2 2 2 2 2 2 2 2 2 2 (1) Silica Zeosil 1165MP from Rhodia. (2)Catenex ® SBR from Shell. (3) Polylimonene. (4) “Si69” from Degussa. (5)N-(1,3-Dimethylbutyl)-N′-phenyl-p-phenylenediamine. (6) Antiozone fromRepsol. (7) N-Cyclohexyl-2-benzothiazolesulphenamide.

The following procedure is used for the tests which follow:

Each of the compositions is produced, in a first step, bythermomechanical working and then, in a second finishing step, bymechanical working.

The elastomer, two-thirds of the silica, the coupling agent, thediphenylguanidine and the carbon black are introduced into a laboratoryinternal mixer of “Banbury” type which has a capacity of 400 cm³, whichis 72% filled and which has an initial temperature of 90° C.

The thermomechanical working is carried out by means of blades, the meanspeed of which is 50 rev/min and the temperature of which is 90° C.

After one minute, the final one-third of the silica, the antioxidant,the stearic acid, the antiozone wax, the MES oil and the resin areintroduced, still under thermomechanical working.

After two minutes, the zinc oxide is introduced, the speed of the bladesbeing 50 rev/min.

The thermomechanical working is carried out for a further two minutes,up to a maximum dropping temperature of approximately 160° C.

The mixture thus obtained is recovered and cooled and then, in anexternal mixer (homofinisher), the sulphur and the sulphenamide areadded at 30° C., the combined mixture being further mixed for a time of3 to 4 minutes (second step of mechanical working).

The compositions thus obtained are subsequently calendered, either inthe form of plaques (with a thickness ranging from 2 to 3 mm) or thinsheets of rubber, for the measurement of their physical or mechanicalproperties, or in the form of profiled elements which can be useddirectly, after cutting and/or assembling to the desired dimensions, forexample as semi-finished products for tires, in particular for treads.

Crosslinking is carried out at 150° C. for 40 min.

The results are presented in Table 2 and in FIGS. 1 and 2.

TABLE 2 Rubber results(tan(δ)max 40° C., G*_(10%,40° C.), ML₍₁₊₄₎100°C.): Examples Comparative examples 1 2 3 4 5 6 7 8 9 10 Tan(δ)_(max) 40°C. 0.125 0.123 0.124 0.30 0.22 0.165 0.21 0.225 0.16 0.22G*_(10%,40° C.) 1.83 1.82 1.81 2.62 2.35 1.85 1.87 1.92 1.66 2.04ML₍₁₊₄₎100° C. 92 93 92 77 112 68 62 67 61 105

FIG. 1 shows that compositions 1, 2 and 3, comprising an SBR which isamine-functional at the chain end and aminoalkoxysilane-functional inthe middle of the chain (respectivelydimethylaminopropyltrimethoxysilane (polymer H),diethylaminopropyltrimethoxysilane (polymer I) and hydrolyseddimethylaminopropyltrimethoxysilane (polymer J)), exhibit a lower tan(δ)max 40° C. value than composition 4 comprising control polymer A(non-functional), than composition 5 comprising control polymer B(amine-functional at the chain end) and than compositions 6, 7, 8, 9 and10 respectively comprising control polymer C(aminoalkoxysilane-functional in the middle of the chain(dimethylaminopropyltrimethoxysilane)), polymer D (silanol-functional inthe middle of the chain), polymer E (epoxide+alkoxysilane-functional inthe middle of the chain), polymer F (silanol+polyether-functional in themiddle of the chain) and polymer G (silanol-functional at the chainend). This reflects an improved hysteresis.

The processing of compositions 1, 2 and 3 nevertheless remains entirelyacceptable, in particular in the light of composition A, which comprisesa non-functional elastomer generally used in the formulations forsemi-finished products intended for the preparation of tires.

FIG. 2 shows that compositions 1, 2 and 3 exhibit a tan(δ) max 40°C./G*_(10%, 40° C.) compromise which is offset with respect to the othercompositions and in particular with respect to composition 6 comprisingthe control polymer C (aminoalkoxysilane-functional in the middle of thechain). This reflects an improved stiffness/hysteresis compromise forcompositions 1, 2 and 3 comprising the modified polymers according toembodiments of the invention.

The invention claimed is:
 1. A modified diene elastomer comprising atleast 50% by weight, with respect to the modified diene elastomer, of anentity functionalized in the middle of the chain by an alkoxysilanegroup, bearing a tertiary amine functional group and the silicon atom ofwhich bonds the two pieces of the chain, the chain ends of the modifieddiene elastomer being functionalized to at least 70 mol %, with respectto the number of moles of chain end, by an amine functional group.
 2. Amodified diene elastomer according to claim 1, wherein the entityfunctionalized in the middle of the chain by the alkoxysilane group,bearing a tertiary amine functional group, the silicon atom of whichbonds the two pieces of the chain, the chain ends being functionalizedto at least 70 mol % by an amine functional group, corresponds to thefollowing formula (I):

in which: the symbol E denotes a diene elastomer functionalized to atleast 70 mol % at the chain end by an amine functional group, R₁denotes, as a function of the degree of hydrolysis, a hydrogen atom or alinear or branched C₁-C₁₀ alkyl radical, R₂ is a saturated orunsaturated, cyclic or non-cyclic, divalent C₁-C₁₈ aliphatic hydrocarbongroup or C₆-C₁₈ aromatic hydrocarbon group, R₃ and R₄, which areidentical or different, represent a linear or branched C₁-C₁₈ alkylradical, or else R₃ and R₄ form, with N to which they are bonded, aheterocycle comprising a nitrogen atom and at least one carbon atom. 3.A modified diene elastomer according to claim 2, wherein R₁ represents ahydrogen atom or a methyl or ethyl radical.
 4. A modified dieneelastomer according to claim 2, wherein R₁ represents a hydrogen atom.5. A modified diene elastomer according to claim 2, wherein R₂represents the saturated linear divalent C₃ aliphatic hydrocarbonradical.
 6. A modified diene elastomer according to claim 2, wherein R₃and R₄, which are identical or different, represent a methyl or ethylradical.
 7. A modified diene elastomer according to claim 1, wherein themodified diene elastomer is a copolymer of butadiene and of avinylaromatic monomer.
 8. A modified diene elastomer according to claim1, comprising at least 70% by weight, with respect to the modified dieneelastomer, of the entity functionalized in the middle of the chain bythe alkoxysilane group, bearing a tertiary amine functional group, thesilicon atom of which bonds the two pieces of the chain, the chain endsbeing functionalized to at least 70 mol % by an amine functional group.9. A process for the preparation of a modified diene elastomer asdefined in claim 1, comprising: anionic polymerization of at least oneconjugated diene monomer in the presence of a polymerization initiatorhaving an amine functional group, modification of the living dieneelastomer bearing an active site obtained in the preceding stage by afunctionalization agent, capable of coupling the elastomer chains,bearing at least one tertiary amine functional group and an alkoxysilanefunctional group, which can be hydrolysed to give silanol, with a molarratio of the functionalization agent to the polymerization initiatorwith a value ranging from 0.35 to 0.65.
 10. A preparation processaccording to claim 9, wherein the polymerization initiator comprises anamine functional group chosen from lithium amides obtained from asecondary amine, and from an organolithium compound.
 11. A preparationprocess according to claim 9, wherein the functionalization agentcorresponds to the formula:

in which: R₂ is a saturated or unsaturated, cyclic or non-cyclic,divalent C₁-C₁₈ aliphatic hydrocarbon group or C₆-C₁₈ aromatichydrocarbon group, R₃ and R₄, which are identical or different,represent a linear or branched C₁-C₁₈ alkyl radical, or else R₃ and R₄form, with N to which they are bonded, a heterocycle comprising anitrogen atom and at least one carbon atom, the linear or branched R′radicals, which are identical to or different from one another,represent a C₁-C₁₀ alkyl group.
 12. A reinforced rubber compositionbased on at least one reinforcing filler and an elastomer matrixcomprising at least one modified diene elastomer as defined in claim 1.13. A rubber composition according to claim 12, wherein the elastomermatrix predominantly comprises the modified diene elastomer as definedin claim
 1. 14. A rubber composition according to claim 12, wherein saidreinforcing filler comprises a reinforcing inorganic filler of siliceoustype according to a fraction by weight of greater than 50% and rangingup to 100%.
 15. A semi-finished article made of rubber for a tire,comprising a crosslinkable or crosslinked rubber composition accordingto claim
 12. 16. A tire comprising a semi-finished article as defined inclaim
 15. 17. A modified diene elastomer according to claim 6, whereinR₃ and R₄ are identical and represent a methyl radical.
 18. A modifieddiene elastomer according to claim 7, wherein the modified dieneelastomer is an SBR.
 19. A preparation process according to claim 10,wherein the secondary amine is a cyclic secondary amine.
 20. Apreparation process according to claim 11, wherein R₃ and R₄ represent aC₁-C₄ alkyl radical, and the linear or branched R′ radicals represent aC₁-C₄ alkyl group.
 21. A modified diene elastomer according to claim 1,wherein the alkoxysilane group is partially or completely hydrolysed togive silanol.